[en] Highlights: • NiAl-NO₃-LDH and NiAl-CO₃-LDH were purposefully fabricated by HMT hydrolysis. • Proper acid-base activity sites were tunably established on NiAl-LDHs. • Acidic sites stemming from low coordination Ni²⁺ in NiAl-NO₃-LDH were confirmed. • The inherent law of pH orienting the establishment of activity sites was revealed.

[en] Recently, Hu et al. [1]. published a paper with the above title. In section 'Effect of contact time', the authors stated, 'In order to study the sorption rate constant of Ni(II) to goethite, the pseudo-second-order rate equation was used to fit the kinetic sorption of Ni(II) to goethite' and referred to two self-citations published in 2008 and 2010 respectively [2, 3]. In fact, this kinetic model has already been published first in 1996 [4], and a modified model was presented in the following years to correct a mistake in the 1996 paper [5-7]. However the mistake in the model was duplicated by other researchers [8, 9]. In order to stop the proliferation of the mistake a comment has been made [10]. This type of error could be avoided if authors have had paid more attentions to details about the model from the original paper [11]. Accuracy in citing references is very important for the transmission of scientific knowledge. Citation errors reflect poorly on authors who republish original ideas that were already published. Hopefully, the identification of this type of problems will lead to improved accuracy in referencing [12]. Authors should make serious efforts to check the accuracy of references cited in their manuscripts as well as to read the original article before quoting it rather than citing from abstracts or cross-references [13]. It is recommended that more attention should be paid in preparing bibliographies and in checking quoted references [14]. (author)

[en] This article is devoted to nickel state in ammonia solutions. Thus, the calculation of equilibrium concentrations of nickel ions in the system Ni²⁺-NH₃-H₂O is conducted.

[en] Studies on the molecular construction and structures of M(NO_3)_2 (M = Cu(II), Ni(II)) complexes with 1,2-bis(dimethyl- 3-pyridylsilyl)ethane (L) have been carried out. Formation of each molecular skeleton appears to be primarily associated with a suitable combination of bidentate N-donors of L and coordinating nature of octahedral metal(II) ions: [Cu(NO_3)_2(L)_2] yields a 2-dimensional sheet structure consisting of 44-membered Cu_4L_4 skeleton whereas [Ni(L)_2(H_2O)_2](NO_3)_2 produces an interpenetrated 3-dimensional structure consisting of 66-membered cyclohexanoid (M_6L_6) skeleton. The Cu(II) ion prefers nitrate whereas the Ni(II) ion prefers water molecules as the fifth and the sixth ligands

[en] The biosorption characteristics of nickel(II) ions using the brown algae (Cystoseria indica, Nizmuddinia zanardini, Sargassum glaucescens and Padina australis) were investigated. Experimental parameters affecting the biosorption process such as pH level, contact time, initial metal concentration and temperature were studied. The equilibrium data fitted very well to the Langmuir adsorption model in the concentration range of nickel(II) ions and at all the temperatures studied. Evaluation of the experimental data in terms of biosorption dynamics showed that the biosorption of nickel(II) onto algal biomass followed the pseudo-second-order dynamics well. The calculated thermodynamic parameters (ΔG^o, ΔH^o and ΔS^o) showed that the biosorption of nickel(II) ions were feasible, spontaneous and endothermic at the temperature ranges of 293-313 K.

[en] In this work, adsorption of Ni(II) from aqueous solution onto hematite under various solution chemistry and temperature was investigated. The results indicated that the pseudo-second-order rate equation fitted the kinetic adsorption well. The adsorption of Ni(II) onto hematite was strongly dependent on pH and ionic strength. At low pH, the adsorption was dominated by outer-sphere surface complexation or ion exchange, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH. A positive effect of FA on Ni(II) adsorption was found at pH < 8.0, whereas a negative effect was observed at pH > 8.0. The Langmuir, Freundlich, and D-R models were applied to simulate the adsorption isotherms at three different temperatures of 293.15, 313.15 and 333.15 K. The thermodynamic parameters were calculated from the temperature dependent adsorption, and the results indicated that the adsorption was endothermic and spontaneous. (author)

[en] Ni 63, a beta radiation source, is prepared by the electrical deposition of radioactive Ni 63 ions on a thin non radioactive nickel foil or Cu plate. Given a half life of 100 years, a nuclear battery will still produce half of its initial starting power after 100 years. A speck of a radioisotope like nickel 63, for example, contains enough energy to power a nano nuclear battery for decades, and to do so safely. Ni 63 plating is similar to other electroplating processes that employ soluble metal anodes. It requires the passage of a direct current between two electrodes that are immersed in a conductive, aqueous solution of nickel salts. The charged Ni ions are formed by sulfate, sulfamate, chloride, and a Watts bath. However, the charged Ni 63 ions are formed by dissolving metal Ni 63. To established the coating condition of Ni 63, non radioactive metal Ni particles are dissolved an acid solution and electroplated on a Ni sheet. The nickel plating process is used extensively for decorative, engineering and electro forming purposes because the appearance and other properties of electrodeposited nickel can be varied over a wide range by controlling the composition and operating parameters of the plating solution. A continuous increase in the grain size versus current density has also been recognized in the direct current electrodeposition of nickel coating. On the other hand, A runa et al. reported that the current density has no significant effect on the grain size of nickel electro deposits. A review of the literature shows that saccharin has often been added to a nickel plating bath since the 1980s to improve the ductility and brightness, and in later periods as a grain refiner agent. In the present paper, not only the preparation of a Ni plating solution prepared by dissolving metal particles, but also an optimization of the deposition conditions, such as the current density, saccharin concentration in the bath, and different metal substrates were investigated. The proposed model can also be applied for radioactive Ni 63 electroplating

[en] Sorption of radionickel on attapulgite is studied as a function of contact time, ionic strength, pH and temperature. The results indicate that the sorption of Ni(II) on attapulgite is strongly ionic strength-dependent at pH <8, and independent of ionic strength at pH >8. Outer-sphere surface complexation or ion exchange contributes to Ni(II) sorption on attapulgite at pH <8, whereas the sorption of Ni(II) is mainly dominated by inner-sphere surface complexation at pH >8. The sorption of Ni(II) on attapulgite increases with increasing temperature, and the thermodynamic parameters (ΔH⁰, ΔG⁰ and ΔS⁰) calculated from the temperature dependent sorption isotherms suggest that the sorption of Ni(II) on attapulgite is a spontaneous and endothermic process. The high sorption capacity of attapulgite suggests that attapulgite is a suitable material for the preconcentration and solidification of radionickel from large volumes of aqueous solutions. (author)

[en] In our published paper entitled 'Sorption of radionickel to goethite: effect of water quality parameters and temperature' published in JRNC 285 (2010) 389-398 [1], the sorption of radionickel to goethite as affected by various environmental conditions such as pH, humic substances, ionic strength and temperature on radionickel sorption has been investigated by using batch technique. The sorption mechanism of radionickel on goethite was discussed according to the experimental data and the fitting results of sorption isotherms by Langmuir, Freundlich and D-R models. Kinetic sorption data was fitted by a pseudo-second-order rate equation. Ho et al. firstly reported the pseudo-second-order rate equation [2, 3], and then further developed this frame work in their following works [4, 5]. In our previous research, we had ever cited the original paper about the sorption isotherms such as Langmuir or Freundlich models. However, the reviewers gave the comments that the models had been widely used and it was not necessary for us to cite the original paper about the sorption isotherm. Similar condition can be also observed for carbon nanotubes that there are a lot of papers about carbon nanotubes not citing the original paper reported by Iijima [6]. In our published paper [1], we think that the pseudo-second-order rate equation has been widely applied and the equation is now a famous model to fit the sorption kinetic data. However, it is essential for us to cite all the relative references accurately so as to transmit scientific knowledge more effectively. We are so sorry to the fact that the original papers [2, 3] were not cited in our published paper [1], but it is not meant to show the disrespect to the author Ho [2]. In our future work, we wish to cite the papers published by Ho whose work are interesting and useful to simulate the sorption kinetic data of metal ions at solid-water interfaces. The physicochemical behavior of radionickel in environment is quite important to understand the potential pollution of radionickel in natural environment. In our published paper [1], the macroscopic data is helpful to understand the sorption mechanism of radionickel at solid-water interfaces. However, the information at microscopic level such as microstructures and chemical species of radionickel can be more accurate to assess the potential physicochemical behavior of radionickel in the environment. This information can be obtained from spectroscopy studies such as XPS, TRLFS and EXAFS. (author)

[en] Magnetic nanoparticles (NPs) studied in hyperthermia investigations have shown promising results in combating tumors and slowing cancerous growth. However, no attention has been paid to hyperthermia properties of nickel ferrite NPs with different compositions. Herein, we synthesize Ni_xFe_3−xO₄ (0 ≤ x ≤ 1) NPs using a co-precipitation method, followed by the investigation of their structural, magnetic, and hyperthermia properties. According to room-temperature hysteresis loop results, the complete replacement of Fe cations by Ni²⁺ ions leads to a reduction in the saturation magnetization (M_s) from 55.40 to 19.30 emu/g, and an increase in the coercive field (H_c) from 7.33 to 71.40 Oe. Moreover, first-order reversal curve analysis reveals a reduction in the respective superparamagnetic fraction from 77 to 29% when increasing the Ni concentration (x) from 0 to 1. The results on magnetic hyperthermia properties show that Ni_0.6Fe_2.4O₄ and Ni_0.8Fe_2.2O₄ NPs have highest heating efficiency, giving rise to specific loss power values of 170.5 and 169 W/g in a water medium with a concentration of 3 mg/ml, and 200.5 and 198.4 W/g for a concentration of 1.5 mg/ml, respectively.